Polysilicon (poly-Si) thin-film transistors (TFTs) have been used in a flat-panel display such as an active matrix liquid crystal display (AMLCD) panel. The channel films for this type of display are typically deposited in the amorphous phase and then crystallized to form smooth, large grain polysilicon. In particular, solid-phase crystallization (SPC) is a promising technique for converting amorphous silicon (a-Si) into polysilicon. The crystallization from an amorphous phase to a poly-crystalline phase occurs through a nucleation process and a grain growth process. In a SPC Si system, it is desirable to achieve the largest possible grains, and therefore, it is desirable to suppress nucleation relative to grain growth. For that reason, SPC is typically carried out in low temperature. SPC using low-temperature furnace annealing requires very long anneal times and thus reduces the throughput of the product. Furthermore, crystalline defects detrimentally effect the performance of TFTs. While rapid thermal annealing (RTA) can increase the throughput, the performance of the TFT using RTA poly-Si is poorer than low-temperature crystallization. Voutsas et al. (U.S. Patent Publication No. 2004/0180481 A1) discloses a method for producing TFTs on a flexible substrate, wherein high-temperature oxidation is applied to a SPC poly-Si material in order to achieve poly-Si of a higher quality. However, this process requires temperatures in the range of 900 to 1150° C.
Laser annealing is another low-temperature annealing technique for converting a-Si into poly-Si. With laser annealing, the electron mobility is high and the overall quality of poly-Si is good. However, due to the instability if the laser beam, the poly-Si area so produced usually has perceptible non-uniformity known as laser mura. For this reason, poly-Si produced by laser annealing is generally not suitable for high-quality display panels.